More from WebMD

Aug. 25, 2011 -- Mutations in a single gene MED12 occur in about 70% of uterine fibroids, Finnish researchers find.

"This is a giant step toward understanding why fibroids arise -- but toward design of targeted therapies it is a very early step," study leader Lauri A. Aaltonen, MD, PhD, of the University of Helsinki, says in a news release. "Let's hope that this journey has begun."

Fibroids, also known as leiomyomas, are noncancerous growths of the uterus. As many as 60% of women develop fibroids by age 45.

In about half of all cases, fibroids cause problems. This may be because of their size, their location in the uterus, or the number of fibroids. Symptoms can include abnormal vaginal bleeding, painful menstruation, abdominal pain, and pain during sex. They can also lead to infertility. Fibroids are the most common reason for hysterectomy -- surgical removal of the uterus.

Previous research has linked several genetic changes to fibroids. But these occur only in a minority of cases, so Aaltonen's team searched for much more common genetic alterations.

They examined 18 fibroids collected from 17 patients. Using a technique called exome sequencing, they compared all protein-coding genes in the fibroids to those of normal tissue. Ten of those 18 fibroids displayed a mutation.

When the researchers examined an additional 207 fibroids from 80 patients, their analysis confirmed the "striking frequency" of the genetic mutations of MED12. Based on their findings, they conclude that such mutations likely play a key role in the development of fibroids.